title: Impact of seasonality and annual immunization of elderly people upon influenza-related hospitalization rates.
abstract: OBJECTIVE
  The objective of this study was to estimate the impact of seasonality and immunization on hospitalization rates of elderly people in a southern Brazilian state.
  
  
  METHODS
  An epidemiological study of ecological design, combining time-series in the period 1995-2009, was carried out. The medical records of individuals residing in Santa Catarina aged≥60 years were obtained from the Hospital Information System of the Brazilian National Health System. Multiple linear regression analysis was used to calculate the impact exerted by seasonality and by influenza immunization coverage on hospitalization rates.
  
  
  RESULTS
  A decrease of 5.73% in the rate of hospitalization was observed in the first quarters of the years, and an increase of 8.75% in the third quarters of the years, showing the impact of seasonality. The results also showed that as the vaccination coverage rate increased 1%, a decrease of 0.1% was observed in the hospitalization rate.
  
  
  CONCLUSIONS
  Seasonality and immunization had an impact on the hospitalization rates of individuals aged≥60 years in the state of Santa Catarina during the period studied.
authors.affiliation: Post-Graduation Program in Health Sciences, University of Southern Santa Catarina, Avenida José Acácio Moreira, 787 Dehon, 88704-900 Tubarão SC, Brazil.
authors.forename: Alana Patrício Stols
authors.initials: AP
authors.lastname: Cruzeta
authors.forename: Ione Jayce Ceola
authors.initials: IJ
authors.lastname: Schneider
authors.forename: Jefferson
authors.initials: J
authors.lastname: Traebert
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001938:Brazil / Q000453:epidemiology; D006760:Hospitalization; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology*; D008875:Middle Aged; D012621:Seasons; D014611:Vaccination
keywords: Aging; Hospital morbidity; Influenza; Vaccination